1. Field of the Invention
The present invention relates to a catalyst used for producing dimethylether, a method of producing the same, and a method of producing dimethylether using the same, and more particularly, to a catalyst used for producing dimethylether, a method of producing the same, and a method of producing dimethylether using the same, capable of increasing a conversion rate of carbon monoxide and a production amount of dimethylether by mixing a methanol synthesis catalyst which is produced by adding one or more promoters to a CuO—ZnO—Al2O3-based main catalyst in order to increase a degree of dispersion of a Cu metal acting as a catalytic active point, with a dehydration catalyst in which Aluminum Phosphate is mixed with gamma alumina, when dimethylether is produced by synthesizing methanol from a synthesis gas containing hydrogen, carbon monoxide, and carbon dioxide and by dehydrating the methanol.
2. Description of the Related Art
Dimethylether is an oxygen-containing compound which has been recently found. Physical and chemical characteristics of dimethylether are similar to those of a liquified petroleum gas (LPG). However, the dimethylether is rather superior to LPG in several aspects. Therefore, the dimethylether can be used as aerosol propellants, a substitute for a diesel fuel, and an intermediate material in a chemical reaction.
As a representative method of synthesizing dimethylether, there is a method of reacting methanol with a strong sulfuric acid catalyst. However, this method has many problems in cost and stability. Namely, high cost is required to reproduce sulfuric acid, and explosion may occur by reacting sulfuric acid with water generated during reaction due to a characteristic of sulfuric acid. As a method capable of overcoming such problems as well as producing the dimethylether in industrial scale, there is a method of collecting the dimethylether in high purity required in aerosol field, by dehydrating methanol using a solid acid dehydration catalyst in a fixed bed reactor and distilling a product thereof.
However, in order to use the dimethylether as the substitute for the diesel fuel, the dimethylether needs to be commercially supplied at a low price. The dimethylether obtained through a dehydration reaction of methanol under the presence of an acid catalyst is formed by synthesizing the methanol from a synthesis gas and performing an acid catalyst reaction. Therefore, the dimethylether is very much higher in price than methanol. In addition, the methanol synthesis reaction is limited thermodynamically to a conversion rate in characteristic thereof.
In order to solve this problem, there is developed a method of synthesizing dimethylether directly from a synthesis gas using a mixed catalyst in which a methanol synthesis catalyst is mixed with an acid catalyst of a dehydration reaction. In the process of synthesizing the dimethylether using the mixed catalyst, the methanol is removed through the dehydration reaction, and water obtained in the process of the dehydration reaction is removed through a water reaction. Therefore, the characteristic of the catalyst is improved, and the conversion rate of carbon monoxide and the yield of dimethylether increase. That is, in the process of reaction of synthesizing the dimethylether directly from the synthesis gas, three reactions (the methanol synthesis reaction, the water gas shift reaction, and the dehydration reaction) are performed simultaneously in the mixed catalyst. The reactions that are performed simultaneously compensates for the problems of the other reactions to solve the problems chemically.
Many producing methods including a method of synthesizing the dimethylether directly from hydrogen and carbon oxide are disclosed in documents. The methods of producing the dimethylether directly from a synthesis gas containing hydrogen, carbon monoxide, and carbon dioxide using a methanol catalyst and a dehydration catalyst together in a fixed bed reactor are disclosed in German Patent No. 291,937, U.S. Pat. Nos. 5,254,596, 4,417,000, 4,177,167, 4,375,424, and 4,098,809, European Patents Nos. 164,156 and 409,086, UK Patents Nos. 2,093,365, 2,097,382, and 2,099,327, German Patents Nos. 3,220,547, 3,201,155, 3,118,620, 2,757,788, and 2,362,944, Danish Patents Nos. 6031/87, and 2169/89, Japanese Patents Nos. 04334445 and 0399489, and Chinese Patent Nos. 1356163.
As a catalyst of the methanol synthesis reaction, a three-phase catalyst is mainly used. In the three-phase catalyst, Cu metal is used as a main material, and materials such as zinc, alumina, chromium, titanium, and the like are used to change a support, and oxides mixed at the several ratio is used. The catalyst represents an activity with respect to not only a water reaction but also an inverse water reaction. In addition, an acid catalyst is used mainly in the dehydration reaction of methanol. As an example of the acid catalyst, there are alumina, zeolite, silica/alumina, metallic salt, an ion exchange resin, and a mixed metal oxide. In dimethylether synthesis process using the mixed catalyst, a characteristic of a promoter in the mixed catalyst has great influence on a conversion rate of a synthesis gas and a selectivity and a yield of a product.
Recently, instead of a method of using by mixing physically such a promoter and a methanol synthesis catalyst, there is proposed a method of using a catalyst in which effective components are synthesized through co-precipitation. For example, in U.S. Pat. No. 4,328,129, a catalyst in which rhodium of 3 wt % and molybdenum of 6.5 wt % are immersed in gamma alumina support is used. Under the condition of 230 psi and 220 to 280° C., when reactant composition is CO:H2=1:2, a conversion rate of synthesis gas into dimethylether and methanol was obtained in a range of 27.1 to 57.3% on the basis of carbon monoxide. When reactant composition is CO:H2=1:1, the conversion rate was obtained in a range of 28.2 to 42.2%.
In addition, in U.S. Pat. No. 4,375,424, gamma alumina was immersed in a solution of copper nitrate and zinc nitrate to produce a catalyst. In this case, under the condition of 1700 psi, 100 to 275° C., 3000 GHSV (Gas Hourly Space Velocity), and CO:H2=1:1 of reactant composition, the conversion rate of CO was obtained in a range of 5.8 to 70.4%, and the conversion rate of dimethylether were obtained in a range of 2.8 to 94.4%.
Meanwhile, techniques for improving characteristics of an acid catalyst used in synthesis of dimethylether have actively researched. In addition, techniques for increasing the yield and the selectivity of dimethylether by immersing an active element in gamma alumina have been tried. For example, U.S. Pat. No. 4,595,785 discloses that the dehydration reaction of methanol is performed under the condition of 1034 kPa, 400° C. using catalyst in which 1% titania is immersed in gamma alumina. As a result, a condensate product containing 57.5% dimethylether, 20% of methanol, and 22.5% water was obtained. Korean Patent Application Publication No. 2000-0002477 discloses that an acid catalyst reformed by formaldehyde is used to synthesize dimethylether from synthesis gas so as to obtain a high conversion rate of carbon monoxide and the selectivity and the yield of dimethylether. However, in the process, alkali component with formaldehyde are used, so that the conversion rate of carbon monoxide is still low.